1. Technical Field
The present disclosure relates to an optical imaging system, an image capturing unit and an electronic device, more particularly to an optical imaging system and an image capturing unit applicable to an electronic device.
2. Description of Related Art
In recent years, with the popularity of electronic devices having camera functionalities, the demand of miniaturized optical systems has been increasing. The sensor of a conventional optical system is typically a CCD (Charge-Coupled Device) or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor. As the advanced semiconductor manufacturing technologies have allowed the pixel size of sensors to be reduced and compact optical systems have gradually evolved toward the field of higher megapixels, there is an increasing demand for compact optical systems featuring better image quality.
A conventional optical system employed in a portable electronic product mainly adopts a two-element lens structure. Due to the popularity of mobile terminals with high-end specifications, such as smart phones, tablet personal computers, wearable apparatus and infrared camera, the requirements for high resolution and image quality of present compact optical systems increase significantly. However, the conventional optical systems cannot satisfy these requirements of the compact optical systems.
Other conventional compact optical systems with three-element lens structure are developed to enhance resolution and image quality. However, the refractive power of the optical system is unevenly distributed so that it is unfavorable for reducing the back focal length of the optical system, and therefore it is unfavorable for keeping the optical system compact. Furthermore, the unevenly distributed refractive power is easily overloaded on a single lens element so that it is unfavorable for correcting the aberration and reducing the sensitivity of the optical system.